Duh, I forgot to finish the equation
BB = (OBP*AB - H)/1 - OBP
should be the correct formula.
Using Beltran, again, we get...
BB = (.354*5113 - 1433)/1 - .354
BB = (1810.002 - 1433)/.646
BB = 377.002/.646
BB = 583.5944272
... which still isn't our desired 591, but again, I imagine that's likely due to the rounded OBP we used. His actual OBP is 0.35483871
Using that extended OBP, we get...
BB = 590.2327
EDIT: The discrepancy can be attributed to the calculator I'm using rounding itself after it runs out of places. I'm using a scientific and not a graphing.